1. Field of the Invention
This invention relates to a sewing machine, more particularly to a scissors-type thread-cutting device for a sewing machine, which includes a first blade member and a second blade member that presses against the first blade member and that is movable relative to the first blade member to cut a thread therebetween.
2. Description of the Related Art
Referring to FIGS. 1 and 2, a conventional scissors-type thread-cutting device for a sewing machine is shown to include a base 21 adapted to be fixed on a machine bed 1, a first blade member 22 locked on the base 21 by means of a lock bolt 221, and a movable cutting unit 23. The movable cutting unit 23 includes a sliding member 231 which can be activated by a driving unit 11 to reciprocate on the machine bed 1, and a second blade member 232 which is carried on the sliding member 231 to move relative to the first blade member 22. The aforesaid conventional device suffers from the following disadvantages:
(1) When wearing occurs between the blade members 22, 232, only the angular position of the first blade member 22 can be adjusted. This adjustment does not permit close contact between the blade portions of the blade members 22, 232 to an extent that enables the blade members 22, 232 to perform a cutting action effectively. In this case, the worn blade members 22, 232 must be replaced with new ones.
(2) It is time-consuming to adjust the blade members 22, 232 to achieve close contact therebetween.
(3) The aforesaid conventional device cannot be used on different types of sewing machines due to the fixed angle between the base 21 and the blade members 22, 232.